Inductive Weighing Device Using LC Resonators for Off-Center Load Accuracy
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Solution Overview
Problem
Existing weighing devices face inaccuracies due to off-center object placement and manufacturing deviations in elastic properties, leading to reduced measurement accuracy and flexibility issues, especially in thin designs.
Innovation Solution
A thin personal weighing device with a bottom and top plate separated by resilient elements and LC circuits positioned near the edges, a conductive material coating, and a computation unit to detect inductance variations, allowing for improved accuracy and reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If inductive sensors are positioned at the center between base plate and load plate, then the device structure is simplified, but measurement accuracy deteriorates when load is placed off-center or when spacing elements have different elastic properties
Solution Approach 1:
The patent divides the sensing function into four separate inductive sensors positioned at the corners of the load plate rather than using a single central sensor. Each sensor independently measures the distance between the load plate and base plate at its specific location, allowing the system to detect and compensate for non-uniform deflection and off-center loading through differential measurement of the four sensor readings.
Solution Approach 2:
The patent transitions from a single-point central measurement to a distributed multi-point measurement approach by positioning sensors at the four corners of the load plate. This spatial distribution across two dimensions (X and Y axes) enables the system to capture the complex deformation pattern of the load plate under various loading conditions, effectively adding spatial dimensionality to the measurement capability.
2Length of moving object
If the top plate is made flexible to reduce thickness, then the device becomes thinner and easier to store, but measurement accuracy deteriorates due to plate flexure causing unrelated travel at sensing elements versus spacing elements
Solution Approach 1:
The patent employs four separate inductive sensors positioned at specific locations (corners) of the load plate, each measuring the local distance between the load plate and base plate at its specific position. This localized measurement approach allows the system to account for non-uniform flexure of the thin top plate, as each sensor captures the actual displacement at its location rather than assuming uniform movement across the entire plate.
Solution Approach 2:
The patent replaces traditional mechanical contact-based sensing with inductive sensing that uses electromagnetic fields to measure distance without physical contact. This substitution allows the sensors to accurately measure the position of the flexible top plate at each corner location, compensating for plate flexure effects that would problematic in mechanical sensing systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances measurement accuracy by minimizing errors from off-center placement and flexure, while maintaining a thin design that is easy to store and use, with a thickness of less than 25 mm, and provides a method for calibration to account for manufacturing deviations.
Implementation Method 1
at least four LC circuits each positioned at a vicinity of an edge of one of the top plate or the bottom plate, at least a conductive material coating, arranged on the other of the top plate or the bottom plate, the four LC circuits and the at least conductive material coating exhibiting an inductance; wherein during operation of the weighing device a movement of the at least conductive material coating relative to each of the four LC circuits along the third direction introduces a variation of the inductance
Data Source
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AI summary
A thin personal weighing device comprising a bottom plate, extending along a reference plane, a top plate movably mounted with regard to the bottom plate along a direction perpendicular to the reference plane, four resilient elements directly interposed between the top and the bottom plate, four LC circuits positioned at a vicinity of an edge of the bottom plate, and a conductive material coating, arranged on the top plate, the four LC resonators and the at least conductive material coating exhibiting an inductance. Movement of the conductive material coating relative to each of the four LC resonators introduces a variation of the inductance. A computation unit detecting the variations of the inductance is electronically coupled with the LC resonators and configured to correlate the variations of the inductance with an actual weight placed on the weighing device. The thickness of the weighing device is less than 25 mm.